Method of forming a joint between a metal rail and a hollow metal rung



Oct. 18, 1966 A. w. MINSHALL 3,279,051 METHOD OF FORMING A JOINT BETWEENA METAL Filed July 21, 1965 RAIL AND A HOLLOW METAL RUNG 2 Sheets-Sheet1 FIG. 5

INVENTOR. AUBREY W MINSHALL A tome Oct. 18, 1966 w. MINSHALL 3,279,051

A. METHOD OF FORMING A JOINT BETWEEN A METAL RAIL AND A HOLLOW METALRUNG Filed July 21, 1965 2 Sheets-Sheet 2 INVENTOR. AUBREY W. M/NSHALLAttorney United States Patent METHOD OF FORMING A JOINT BETWEEN A METALRAIL AND A HOLLOW METAL RUNG Aubrey Wilson Minshall, 3114 ConstitutionBlvd., Cooksville, Ontario, Canada Filed July 21, 1965, Ser. No. 473,750

Claims priority, application Canada, Apr. 5, 1965, 927,327 1 Claim. (Cl.29-512) This invention relates to a method of making a ladderconstruction and particularly to an improved method of making a metalladder construction. The invention has particular relation to joininghollow ladder rungs to side rails and where such parts are made fromaluminum alloys.

Various side rail and rung connections have been previously employed inmetal ladder constructions but to meet the requisite strength under theapplication of torque it has generally been necessary to incorporateadditional members in the joint between the cross rung and side rails;these additional members increase the expense of production and,furthermore, undesirably increase the Weight of a metal ladder whenconstructed of aluminum alloys.

It is an object of the invention to provide a method of making a ladderjoint construction which utilizes only the body of material which formsthe ladder rung and side rail and wherein no additional material orparts are incorporated.

It is a further object of the invention to provide a method of making aladder joint construction which will ensure freedom from failure uponapplication of the minimum torque stipulated for safety requirements andwherein said joint incorporates only the material of the body of theladder rung and side rail.

The invention will now be described with reference to the accompanyingdrawings, in which:

FIGURE 1 is a side view, partly in section, illustrating a preferredmanner of swaging a hollow rung adjacent its ends;

FIGURE 2 is a view in section illustrating the step of blanking a siderail;

FIGURE 3 is a perspective view of a preferred configuration of the blankproduced by the step illustrated in FIGURE 2;

FIGURE 4 is a view in section illustrating the step of forming a flangeto the blank illustrated in FIGURE 3;

FIGURE 5 is a view in section showing a flanged side rail and swagedrung in assembled relation prior to the joining step;

FIGURE 6 is a view in section illustrating the step of coin curling theassembled side rail and swaged rung to form the joint;

FIGURE 7 is a perspective view with part cut away of the joint of theside rail and rung produced according to the invention; and

FIGURE 8 is a perspective view looking towards the inner side of theladder of an assembled rung and side rail produced according to theinvention.

Referring now to the drawings a rung 10 is provided with a shoulder 12which extends across the perimeter of the rung 10; the shoulder 12 beingpositioned adjacent one end of the rung 10 leaving an extending outwardportion 14. It will be appreciated that a corresponding shoulder 12 willbe provided adjacent the other end of the rung 10. To provide bothshoulders simultaneously a preferred manner of performing this swagingoperation is shown in FIGURE 1; the rung 10 is positioned between a pairof clamps 16 operated by a piston and cylinder structure 18; the ends ofthe clamps 16 terminate some distance short of the ends of the rung 10and hollow dies 3,279,051 Patented Oct. 18, 1966 20 of innerconfiguration corresponding to the outer configuration of the rung 10are positioned over each end of the latter. The length of each die 20 issuch that its open end terminates short of the adjacent end of theclamps 16 when the end of the rung 10 bears against the base 22 of therespective die 20. A cylinder and piston structure 24 is connected toeach die 20 and when the clamps 16 closeonto the rung 10 the step ofproviding the shoulders 12 is completed by actuating the dies 20 inwardsto swage the rung 10.

As illustrated in FIGURE 2 the base 26 of the side rail 28 is blankedout by means of a press tool 30 cooperating with a support 32 to providea cavity 34 somewhat smaller in diameter than the outward portion 14 ofthe rung 10. The illustrated side rail 28 is intended for a constructionof an extension ladder and has outwardly extending flanges 36 and 38,the latter terminating in an inturned member 40. The word outwardlydesignates a direction away from the rungs 10 in the assembled ladderbut the invention is equally applicable to a single ladder wherein theside rail 28 is constructed of a plane memher.

As illustrated in FIGURE 3 the preferred shape formed during blanking bythe head of the press tool 30 and cooperating support is such that thecircular cavity 34 communicates with radially oriented equally spacedchannels 42 of uniform width along their length, thereby providingtongues 44 which taper in the direction of the cavity 34. The length ofeach of the channels 42 is such that their bases 46, each of which ispreferably rounded, rest on the perimeter of a circle whereby thetongues 44 are less than the length of the outward portion 14 of therung 10. Furthermore, it is preferable for the bases 46 to rest on theperimeter of a circle having a diameter slightly less than the outsidediameter of the peripheral shoulder 12.

As illustrated in FIGURE 4 the material adjacent the edge of the cavity34 is formed outwardly of the base 26 to provide a flange 48 whichpreferably has a diameter slightly less than the diameter of the rung 10and at least no greater than the outside diameter of the peripheralshoulder 12. Furthermore, the amount of material formed at the edge ofthe cavity 34 is such that the depth of the flange 46 is less than thelength of the outward portion 14 of the rung 10. In the preferredblanked configuration wherein the tongues 44 are provided thisrelationship of the depth of the flange 46 to the length of the outwardportion 14 will result if the perimeter of the head of the press tool 30corresponds with the perimeter prescribed by the bases 46 of thechannels 42; also the flanging operation of the tongues 44 will be lesssevere as compared with a flange 46 produced from an integral edge withthe result that the amount of work hardening will be reduced thusfacilitating the final step described below in the method of the presentinvention.

After completion of the swaging and flanging steps assembly of the rung10 and the side rail 28 is elfected. As illustrated in FIGURE 5 theoutward portion 14 of the rung 10 is pressed into the flange 48, theoutward end 14 of the rung 10 entering the side rail 28 from the sideopposed to the flange 48. The rung 10 is held by the clamps 16 and anactuated suitably shaped die 50 presses the side rail 28 along theoutward portion 14 until the side rail 28 encounters the peripheralshoulder 12; the assembled relationship of the rung 10 and the side rail28 is such that the outward portion 14 of the rung 10 terminates beyondthe end of the flange 48.

The final step in the method, as illustrated in FIGURE 6, is to bend orcoin curl the outward portion 14 of the rung 10 over the flange 48; thisis conveniently effected by means of an actuated suitably shaped die 52which has a tongue 54 which extends with sliding contact into the rung10 past the shoulder 12 thus providing the requisite support for therung 10 in co-operation with the external clamps 16. At the root of thetongue 54 the surface of the die 52 flares outwardly with respect to itsaxis in an arcuate configuration which terminates in a circular abutment56. When the die 52 is actuated towards the assembled rung 10 and siderail 28, the tongue 54 enters the rung 10 and travels past the shoulder12; the extremity of the outward portion 14 then meets the arcuateconfiguration at the root of the tongue 54 and due to the arcuateconfiguration commences to bend over and eventually in the reversedirection towards the side.

rail 28. With continued movement of the die 52 the flange 48 also beginsto bend over in the same direction as the portion 14; the coin curlingaction is continued until the latter meets the side rail 28 and thencompleted when the recess between the root of the tongue 54 and thecircular abutment 56 is filled with the curled over portion 14 with theflange 48.

By way of example a joint of a rung and a rail made according to theinvention was tested under torque and 1,720 inch pounds had to beapplied at which level the rung showed twisting but the joint was stillintact; in contrast a rung which had simply been swaged onto the siderail loosened on the application of a torque of 590 inch pounds.

While certain embodiments have been illustrated and described for thepurpose of disclosure, it will be understood that the invention is notlimited thereto, but contemplates such modifications and otherembodiments as may be utilized without departing from the invention.

I claim:

The method of making an integral joint between a hollow metal rung and ametal side rail part comprising the steps of forming an opening having atoothed flange at its perimeter in said metal side part, swaging saidrung to form a peripheral abutment on its surface adjacent an end, saidabutment being positioned in relation to said end a distance greaterthan the depth of said toothed flange, inserting said rung through saidflange opening whereby said abutment bears against the wall of said siderail opposed to said flange and curl coining in a direction outwards ofthe centre of said opening the metal of said rung between said abutmentand said end over said toothed flange untilsaid end bears against thewall of said side rail opposed to said abutment.

References Cited by the Examiner UNITED STATES PATENTS 1 ,'7 37,780 12/1929 Wagenhorst. 3,068,029 12/ 1962 Schwartz 29523 XR FOREIGN PATENTS587,952 5/ 1947 Great Britain. 845,803 8/ 1960 Great Britain.

CHARLIE T. MOON, Primary Examiner.

